JP4430626B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an apparatus having a function of estimating a fuel property (cetane number) of a fuel in use.

  Patent Document 1 discloses a control apparatus for a compression ignition internal combustion engine that performs premixed combustion. According to this apparatus, the actual ignition timing of the fuel is detected during the premixed combustion, and the ignition timing error that is a difference from the preset standard fuel ignition timing and the variation in the ignition timing error are detected. The property of the fuel is determined.

JP-A-2005-171818

  The engine operating region in which the premixed combustion is performed is relatively narrow when viewed from the whole engine operating region. Therefore, in the above-described conventional apparatus, the execution timing of the fuel property is delayed, the fuel injection timing is not suitable for the fuel property, and misfire may occur. In addition, it is desirable to determine the fuel property by detecting the actual ignition timing many times and using the average value (learned value) of the detection results. However, if the engine operating state changes, accurate ignition timing detection is possible. It is not easy to execute the above for a predetermined number of times.

  The present invention has been made paying attention to this point, and appropriately learns the fuel properties, specifically, the cetane number of the fuel in use, and starts control suitable for the fuel in use at an early stage. It is an object of the present invention to provide a control device for an internal combustion engine that can be used.

In order to achieve the above object, a first aspect of the present invention provides a control device for an internal combustion engine comprising a fuel injection means (6) for injecting fuel into a combustion chamber of the internal combustion engine (1), wherein the fuel injection means injects fuel. and ignition timing detection means for detecting the ignition timing of fuel (CAFM) that is, cetane number of the fuel in use (CE T) estimated in accordance with the ignition timing to be detected (CAFM), the estimated cetane number ( The fuel injection by at least the fuel injection means using the cetane number learning means for calculating the learning value (CETLRN) by performing a smoothing operation of CET) and the learning value (CETLRN) calculated by the cetane number learning means Control means for controlling the engine including timing control, and the cetane number learning means uses the calculated learning value as a temporary learning value (until learning of the cetane number is completed). CETLRNT), and the temporary learning value (CETLRNT) is stored from the time when the cetane number continuous estimation count (CLRN) corresponding to the detected ignition timing (DAFM) reaches the first predetermined value (CL1). When the number of consecutive estimations of the cetane number (CLRN) reaches a second predetermined value (CL2) greater than the first predetermined value (CL1), it is determined that the learning is completed and the learning value (CETLRN) at that time is determined. ) Is stored as a complete learning value (CETLRNC), and the update of the temporary learning value (CETLRNT) is continued until the learning is completed, and the control means continues to update the temporary learning value (CETLRNC) until the learning is completed. The control is performed using CETLRNT, and the control is performed using the complete learning value (CETLRNC) from the time when the learning is completed.

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the learning of the cetane number is performed by the fuel injection means by the fuel injection means when the engine is in an idle operation state immediately after refueling. The cetane number is not learned until the next refueling is performed after completion of the learning .

According to the first aspect of the present invention, the cetane number of the fuel in use is estimated according to the detected ignition timing, and the learned value is calculated by performing the smoothing operation of the estimated cetane number , Engine control including at least control of fuel injection timing by the fuel injection means is performed using the calculated learning value. Until the learning of the cetane number is completed, the calculated learning value is held as a temporary learning value, and control is performed using the temporary learning value until the learning is completed. Therefore, for example, immediately after refueling, there is an extreme difference between the learning value and the actual cetane number compared to the case where control is performed using the previous learning value or a preset learning value until learning is completed. It is difficult to generate and relatively stable control can be performed. In addition, storage of the temporary learning value is started when the cetane number continuous estimation count corresponding to the detected ignition timing reaches the first predetermined value, and the cetane number continuous estimation count is a second predetermined value greater than the first predetermined value. The learning value obtained when the value reaches is stored as a complete learning value and used for control. That is, since it is determined that the learning has been completed when the stable state of the engine operating state continues for a relatively long time and the number of continuous estimations of the cetane number reaches the second predetermined value, the reliability is finally improved. While a high complete learning value can be obtained, relatively stable control can be performed with a provisional learning value that is not as high as the complete learning value but relatively reliable. Further, by continuing to update the provisional learning value until learning is completed, the accuracy of the provisional learning value can be gradually increased even when establishment / non-establishment of the execution condition of cetane number learning is repeated.

According to the second aspect of the present invention, the learning of the cetane number is executed by changing the mode of fuel injection by the fuel injection means when the engine is in the idle operation state immediately after refueling. The cetane number is not learned until refueling .

Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 are diagrams showing the configuration of an internal combustion engine and a control device therefor according to an embodiment of the present invention. The following description will be given with reference to both figures together. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 6 is provided in each cylinder. The fuel injection valve 6 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 4, and the valve opening timing and valve opening time of the fuel injection valve 6 are controlled by the ECU 4.

  The engine 1 includes an intake pipe 7, an exhaust pipe 8, and a turbocharger 9. The turbocharger 9 includes a turbine that is rotationally driven by the kinetic energy of the exhaust, and a compressor that is connected to the turbine via a shaft. The turbocharger 9 pressurizes (compresses) air sucked into the engine 1.

  An intercooler 21 is provided on the downstream side of the compressor of the intake pipe 7, and a throttle valve 22 is provided on the downstream side of the intercooler 21. The throttle valve 22 is configured to be opened and closed by an actuator 23, and the actuator 23 is connected to the ECU 4. The ECU 4 controls the opening degree of the throttle valve 22 via the actuator 23.

  Between the exhaust pipe 8 and the intake pipe 7, an exhaust gas recirculation passage 25 that recirculates exhaust gas to the intake pipe 7 is provided. The exhaust gas recirculation passage 25 is provided with an exhaust gas recirculation valve (hereinafter referred to as “EGR valve”) 26 for controlling the exhaust gas recirculation amount. The EGR valve 26 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 4. The EGR valve 26 is provided with a lift sensor 27 for detecting the valve opening degree (valve lift amount) LACT, and the detection signal is supplied to the ECU 4. The exhaust gas recirculation passage 25 and the EGR valve 26 constitute an exhaust gas recirculation mechanism.

  The intake pipe 7 includes an intake air amount sensor 31 that detects an intake air amount GA, a boost pressure sensor 32 that detects an intake pressure (supercharge pressure) PB on the downstream side of the compressor, and an intake pressure that detects an intake pressure PI. A sensor 33 is provided, and the exhaust pipe 8 is provided with an exhaust temperature sensor 34 for detecting the exhaust temperature TE. These sensors 31 to 34 are connected to the ECU 4, and detection signals of the sensors 31 to 34 are supplied to the ECU 4.

On the downstream side of the turbine of the exhaust pipe 8, a catalytic converter 28 that promotes oxidation of hydrocarbons and the like contained in the exhaust gas, and a particulate matter filter 29 that collects particulate matter (mainly composed of soot). Is provided.
Each cylinder of the engine 1 is provided with an in-cylinder pressure sensor 2 that detects an in-cylinder pressure (combustion pressure). In the present embodiment, the in-cylinder pressure sensor 2 is configured integrally with a glow plug provided in each cylinder. A detection signal from the in-cylinder pressure sensor 2 is supplied to the ECU 4. The detection signal of the in-cylinder pressure sensor 2 actually corresponds to a differential signal with respect to the crank angle (time) of the in-cylinder pressure PCYL, and the in-cylinder pressure PCYL is obtained by integrating the in-cylinder pressure sensor output. .

  The engine 1 is provided with a crank angle position sensor 3 that detects a rotation angle of a crankshaft (not shown). The crank angle position sensor 3 generates a pulse every crank angle, and the pulse signal is supplied to the ECU 4. The crank angle position sensor 3 further generates a cylinder identification pulse at a predetermined crank angle position of the specific cylinder and supplies it to the ECU 4.

  The ECU 4 detects an accelerator sensor 35 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 36 that detects a cooling water temperature TW of the engine 1, and a temperature TOIL of the lubricating oil of the engine 1. An oil temperature sensor 37, an oxygen concentration sensor (not shown) for detecting the oxygen concentration in the exhaust, an intake air temperature sensor (not shown) for detecting the intake air temperature TA of the engine 1, and the like are connected. The detection signal is supplied to the ECU 4.

  The ECU 4 supplies a control signal for the fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1 to the drive circuit 5. The drive circuit 5 is connected to the fuel injection valve 6, and supplies a drive signal corresponding to the control signal supplied from the ECU 4 to the fuel injection valve 6. Thus, at the fuel injection timing corresponding to the control signal output from the ECU 4, fuel is injected into the combustion chamber of each cylinder by the fuel injection amount corresponding to the control signal. The ECU 4 normally executes pilot injection and main injection for one cylinder.

  The ECU 4 includes an amplifier 10, an A / D converter 11, a pulse generator 13, a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 15 that stores a program executed by the CPU 14, and a CPU 14. A RAM (Random Access Memory) 16 for storing calculation results and the like, an input circuit 17, and an output circuit 18 are provided. A detection signal of the in-cylinder pressure sensor 2 is input to the amplifier 10. The amplifier 10 amplifies an input signal. The signal amplified by the amplifier 10 is input to the A / D converter 11. The pulse signal output from the crank angle position sensor 3 is input to the pulse generator 13.

  The A / D converter 11 includes a buffer 12, converts the in-cylinder pressure sensor output input from the amplifier 10 into a digital value (hereinafter referred to as “pressure change rate”) dp / dθ, and stores it in the buffer 12. More specifically, the A / D converter 11 is supplied with a pulse signal PLS1 (hereinafter referred to as “1 degree pulse”) PLS1 having a crank angle of 1 degree from the pulse generator 13, and this 1 degree pulse PLS1. The in-cylinder pressure sensor output is sampled at a period of

  On the other hand, the pulse signal PLS6 with a crank angle of 6 degrees is supplied from the pulse generator 13 to the CPU 14, and the CPU 14 performs a process of reading the digital value stored in the buffer 12 with the period of the 6 degrees pulse PLS6. . That is, in this embodiment, the A / D conversion unit 11 does not issue an interrupt request to the CPU 14, but the CPU 14 performs a reading process at a cycle of the 6-degree pulse PLS6.

  The input circuit 17 converts detection signals from various sensors into digital values and supplies them to the CPU 14. The engine speed NE is calculated from the cycle of the 6-degree pulse PLS. Further, the required torque TRQ of the engine 1 is calculated according to the accelerator pedal operation amount AP.

  The CPU 14 outputs a control signal for controlling the throttle valve 22, the EGR valve 26 and the like through the output circuit 18 in accordance with the engine operating state. Further, the CPU 14 executes processing for learning the cetane number of the fuel in use as described below, and performs fuel injection control and exhaust gas recirculation amount control according to the learned cetane number.

  3 and 4 are flowcharts showing the procedure of the cetane number estimation process. In step S11, it is determined whether or not it is immediately after refueling. Immediately after refueling is determined based on the increase in the fuel meter, the opening / closing of the filler cap, and the change of the engine switch from OFF to ON. If the answer to step S11 is affirmative (YES), the learning flag FLRN is set to “0” (step S12). The learning flag FLRN is set to “1” when learning of the cetane number is completed (see step S34). If it is not immediately after refueling, the process immediately proceeds from step S11 to step S13.

  In step S13, it is determined whether or not the learning flag FLRN is “1”. If the answer is affirmative (YES), an estimated wall temperature of the combustion chamber (hereinafter simply referred to as “wall temperature”) TWALL is set. Calculate (step S16). Specifically, the basic value is calculated according to the fuel injection amount TOUT and the engine speed NE, and the basic value is corrected according to the engine coolant temperature TW, the engine oil temperature TOIL, the exhaust gas temperature TE, and the intake air temperature TA. To calculate the wall surface temperature TWALL. The wall surface temperature TWALL is referred to in step S17.

  In the subsequent step S22, the value of the counter CLRN is set to “0”. Thereafter, this process is terminated. The counter CLRN is a counter that counts the number of times of continuous calculation of the estimated cetane number CET, is incremented in step S29 described later, and is referred to in steps S30 and S31.

  If FLRN = 0 in step S13 and cetane number learning has not been completed, it is determined whether or not a predetermined time TSF (for example, 2 minutes) has elapsed since the engine 1 was started. The predetermined time TSF is set according to the time required for the remaining fuel in the fuel supply system to be completely replaced after refueling. If the answer to step S14 is negative (NO), the process proceeds to step S16.

When the predetermined time TSF has elapsed after the engine 1 is started, the process proceeds to step S15 to determine whether or not the engine 1 is in an idle state. If this answer is negative (NO), the process proceeds to step S16.
When the operating state of the engine 1 is the idle state, the process proceeds from step S15 to step S17, and it is determined whether or not the wall surface temperature TWALL is lower than a predetermined temperature TWLTH (for example, 100 ° C.). If this answer is affirmative (YES), the process proceeds to step S20.

If TWALL ≧ TWLTH in step S17, the system waits for a predetermined time ΔTWAIT (for example, 30 seconds) (step S18), and lowers the wall surface temperature TWALL by the set decrease amount ΔT (step S19). Thereafter, the process returns to step S15. The setting decrease amount ΔT is set larger as the wall surface temperature TWALL is higher.
If Steps S17 to 19 are repeatedly executed and the answer to Step S17 is affirmative (YES), the process proceeds to Step S20.

  In step S20, it is determined whether or not the glow plug is being energized. If the answer is affirmative (YES), the process proceeds to step S22. When the glow plug is not energized, the process proceeds to step S21 to determine whether or not a predetermined execution condition for stably executing the cetane number estimation is satisfied. The predetermined execution condition is, for example, that the exhaust temperature TE is equal to or higher than a predetermined temperature TE0 (for example, about 90 ° C.), and the cooling water temperature TW or the oil temperature TOIL indicating the warm-up state of the engine 1 is equal to or higher than the predetermined temperature TWUP (for example, 80 ° C.). It is established when If the answer to step S21 is negative (NO), the process proceeds to step S22.

  When the predetermined execution condition is satisfied, the process proceeds from step S21 to step S23, where pilot injection is stopped and single injection is performed. That is, the number of fuel injections NINJ per cylinder is set to 1, and the main injection timing is changed from the normal direction to the advance direction (step S24). Thus, by making the fuel injection as single injection and advancing the fuel injection timing from the usual, it is possible to easily detect the difference in ignition timing due to the difference in cetane number.

  In step S25, a CAFMM map (not shown) is searched according to the engine speed NE and the required torque TRQ to calculate a reference ignition timing CAFMM. The CAFMM map is set based on, for example, an average cetane number (for example, 47) fuel. In step S26, the ignition delay angle DCA is calculated by subtracting the actual ignition timing CAFM from the reference ignition timing CAFMM.

  FIG. 5 is a block diagram showing a configuration of an ignition timing calculation module that calculates (detects) the actual ignition timing CAFM. The function of the ignition timing calculation module is realized by arithmetic processing by the CPU 14. The ignition timing calculation module includes a band pass filter unit 71, a phase delay correction unit 72, and an ignition timing determination unit 73. The band change filter unit 71 receives the pressure change rate dp / dθ output from the in-cylinder pressure sensor 2. A waveform W1 shown in FIG. 6 represents an input waveform, and a waveform W2 represents an output waveform. Since the phase delay occurs in the band pass filter unit 71, the phase delay correction unit 72 corrects this delay.

  The ignition timing determination unit 73 determines the crank angle position at which the pressure change rate dp / dθ has a peak value as the actual ignition timing CAFM, corresponding to the fuel injection. Specifically, as shown in FIG. 7B, the crank angle at which the pressure change rate dp / dθ output from the phase delay correction unit 72 exceeds the detection threshold DPP is determined as the actual ignition timing CAFM.

  FIG. 7A shows an injection pulse INJM starting from the crank angle CAIM, and FIG. 7B shows an angle range RDET (for example, 10 degrees) for detecting the actual ignition timing CAFM. Yes. Thus, by limiting the detection angle range RDET to a relatively narrow range, it is possible to accurately determine the ignition timing without increasing the calculation load on the CPU 14.

Returning to FIG. 3, in step S27, the ignition delay angle DCA is converted into the ignition delay time TDFM using the engine speed NE, the CET table shown in FIG. 8 is searched according to the ignition delay time TDFM, and the cetane number CET Is calculated. In subsequent step S28, the estimated cetane number CET is applied to the following equation (1) to calculate a cetane number learning value CETLRN.
CETLRN = α × CET + (1−α) × CETLRN (1)
Here, α is an annealing coefficient set to a value between 0 and 1, and CETLRN on the right side is a previously calculated value.

  The cetane number learning value CETLRN is calculated using all the in-cylinder pressure sensor outputs of the four cylinders. Therefore, the cetane number CET detected for each cylinder and the cetane number CET with different detection timings are averaged by the above equation (1).

  In step S29, the counter CLRN is incremented by “1”, and it is determined whether or not the value of the counter CLRN is smaller than a first predetermined value CL1 (for example, 10). If the answer is affirmative (YES), the estimated number of data of the cetane number CET is too small, and thus this process is immediately terminated.

  When CLRN ≧ CL1 in step S30, it is further determined whether or not the value of the counter CLRN is equal to or larger than a first predetermined value CL1 and smaller than a second predetermined value CL2 (for example, 70) (step S31). If this answer is affirmative (YES), the learning value CETLRN is stored as the provisional learning value CETLRNT (step S32).

  If the answer to step S31 is negative (NO), that is, if the value of the counter CLRN is equal to or greater than the second predetermined value CL2, the cetane number learning value CETLRN is stored as the complete learning value CETLRNC (step S33), and the learning flag FLRN is set to “ 1 "(step S34).

  3 and 4, when the predetermined execution condition is satisfied in the idle operation state, the fuel injection is changed to the single injection and the fuel injection timing is changed in the advance direction. The cetane number can be estimated even in the operating state, and the cetane number of the fuel in use can be determined quickly and accurately.

  Further, when the engine 1 is in an operation state other than the idle state, the wall surface temperature TWALL is calculated, and is reduced by a predetermined decrease amount ΔT each time a predetermined time ΔTWAIT has elapsed after shifting to the idle state. When the wall surface temperature TWALL becomes lower than the predetermined temperature TWLTH and the predetermined execution condition is satisfied, the cetane number is estimated. Therefore, when the state immediately shifts from the high load operation state to the idle state, the cetane number is not estimated until the wall surface temperature TWALL becomes lower than the predetermined temperature TWLTH. High estimation can be prevented and an accurate estimated cetane number CET can be calculated.

  Further, when the number of continuous executions of cetane number estimation is smaller than the second predetermined value CL2 and the calculation of the learning value is not completed, the temporary learning value CETLRNT is updated, and the number of continuous executions of cetane number estimation is the second predetermined value. When the value CL2 is reached, the learning value CETLRN at that time is stored as the complete learning value CETLRNC, and learning of the cetane number is completed. As will be described later, until the learning is completed, the provisional learning value CETLRNT is applied to the control of the fuel injection timing and the like, and the complete learning value CETLRNC is applied after the learning is completed.

  According to the processing of FIGS. 3 and 4, the temporary learning value CETLRNT is updated until learning is completed. Therefore, even if the execution / non-establishment of the cetane number learning execution condition is repeated, the temporary learning value is gradually increased. The accuracy of CETLRNT can be increased.

FIG. 9 is a flowchart for explaining control switching according to the cetane number learning value.
In step S41, it is determined whether or not the learning flag FLRN is “1”. If the answer is negative (NO) and the learning is not completed, the control cetane number CETCTL is set to the temporary learning value CETLRNT. (Step S43), and the process proceeds to step S44. When FLRN = 1 and learning is completed, the control cetane number CETCTL is set to the complete learning value CETLRNC (step S42), and the process proceeds to step S44.

  In step S44, it is determined whether or not the control cetane number CETCTL is greater than a first threshold value CETH1 (for example, 44). If the answer is negative (NO), combustion control for low cetane number is executed (step S45). More specifically, the fuel injection timing control and the exhaust gas recirculation amount control are executed using the fuel injection timing map and the target exhaust gas recirculation amount map set for the low cetane number.

  If CETCTL> CETH1 in step S44, it is further determined whether or not the cetane number for control CEETCTL is greater than a second threshold value CETH2 (for example, 52) (step S46). If the answer is negative (NO), that is, if the control cetane number CETLCTL is greater than the first threshold CETH1 and less than or equal to the second threshold CETH2, combustion control for medium cetane number (average cetane number) is executed. (Step S47). More specifically, the fuel injection timing control and the exhaust gas recirculation amount control are executed using the fuel injection timing map and the target exhaust gas recirculation amount map set for the medium cetane number.

  If the answer to step S46 is affirmative (YES), combustion control for high cetane number is executed (step S48). More specifically, the fuel injection timing control and the exhaust gas recirculation amount control are executed using the fuel injection timing map and the target exhaust gas recirculation amount map set for the high cetane number.

  According to the processing of FIG. 9, the combustion control is executed using the provisional learning value CETLRNT before the cetane number learning is completed, and the combustion control is executed using the complete learning value CETLRNC after the cetane number learning is completed. . Thus, for example, immediately after refueling, the learning value and the actual cetane number are more extreme than in the case where control is performed using the previous complete learning value or a preset learning value until learning is completed. It is difficult for deviation to occur, and relatively stable control can be performed until the fully learned value CETLRNC is obtained.

FIG. 10 is a flowchart of a process for detecting that the combustion is unstable (deterioration of Pmi fluctuation rate, occurrence of misfire) and forcibly switching the combustion control selected in the process of FIG.
In step S51, it is determined whether or not the operating state of the engine 1 is in the combustion stability determination region. The combustion stability determination area is an operation area corresponding to a state where the vehicle driven by the engine 1 is traveling at a constant speed at a speed of about 80 to 100 km / h, for example. If the answer to step S51 is negative (NO), the process immediately ends.

  When the engine operating state is in the combustion stability determination region, a combustion stability parameter indicating combustion stability is calculated (step S52). As the combustion stability parameter, the Pmi fluctuation rate (standard deviation of the indicated mean effective pressure Pmi) is generally known, but in this embodiment, the area ratio RS described below is used instead of the Pmi fluctuation rate.

  FIG. 11A shows the transition of the in-cylinder pressure PCYL at the time of normal combustion, and FIG. 11B shows the transition of the in-cylinder pressure PCYL corresponding to the combustion state immediately before the occurrence of misfire, with the Pmi fluctuation rate increasing. . Here, the compression stroke area parameter SCMP indicating the area corresponding to the compression stroke with the right-down hatching in FIG. 11 and the expansion stroke area parameter SXPL indicating the area corresponding to the expansion stroke with the right-up hatching are shown in FIG. The ratio is defined as an area ratio RS (= SCMP / SXPL). This area ratio RS shows a tendency to increase as the combustion state becomes unstable (the Pmi fluctuation rate increases). Therefore, in step S52 in FIG. 10, the area ratio RS is calculated.

In step S53, it is determined whether or not the area ratio RS exceeds the determination area ratio RSTH. If the answer to step S53 is negative (NO), that is, if the combustion state is stable, the process immediately ends.
On the other hand, when the area ratio RS exceeds the determination area ratio RSTH, it is determined that the combustion state is unstable (including misfire), and it is determined whether or not the current combustion control is combustion control for low cetane number. (Step S54). If the answer is affirmative (YES), it is determined that there is some abnormality in the engine, and a warning lamp is turned on (step S55).

  If the answer to step S54 is negative (NO), it is further determined whether or not the current combustion control is a combustion control for medium cetane number (step S56). If this answer is affirmative (YES), the combustion control is forcibly switched to the combustion control for the low cetane number (step S58).

  If the answer to step S56 is negative (NO), that is, if combustion control for high cetane number is being executed, the control is forcibly switched to combustion control for medium cetane number (step S57).

  According to the process of FIG. 10, when combustion instability is detected, the combustion control is forced to control suitable for a fuel having a lower cetane number as in the case where the control cetane number CETCTL is decreased. Can be switched. If the combustion instability is not resolved even after executing the combustion control for the low cetane number, the warning lamp is turned on. Thereby, the instability of the combustion state due to the fact that the control cetane number CETCTL is not suitable for the actual cetane number of the fuel can be quickly eliminated.

  Further, according to the method of determining the increase in the Pmi fluctuation rate using the area ratio RS, it is possible to perform determination that is not affected by the detection accuracy of the in-cylinder pressure sensor 2.

  FIG. 12 is a time chart showing the transition of the engine coolant temperature TW immediately after the cold start of the engine 1. When the cooling water temperature TW reaches the predetermined valve opening water temperature TWTHOPN at time t1, the thermostat provided in the cooling water passage is opened, and the cooling water starts to circulate between the engine 1 and the radiator (not shown). Thereafter, the engine coolant temperature TW is substantially constant for several minutes until time t2, and during this time, cetane number learning is performed and a provisional learning value CETLRNT is calculated. However, since the learning time is short, the complete learning value CETLRNC cannot be obtained.

  Thereafter, the engine coolant temperature TW rises and reaches the target coolant temperature TWOBJ at time t3. Thereafter, a radiator fan (not shown) provided in the vicinity of the radiator is driven and controlled so that the engine cooling water temperature TW is maintained at the target water temperature TWOBJ. Through learning after time t3, a complete learning value CETLRNC is calculated. Therefore, according to the present embodiment, combustion control is performed using the provisional learning value CETLRNT from time t2 to time t3, and it is possible to suppress instability of combustion or increase in the amount of particulate matter generated immediately after refueling. it can.

  FIG. 13 is a time chart showing the transition of the estimated cetane number CET when the engine 1 shifts from the non-idle operating state (hereinafter referred to as “off-idle operating state”) to the idle operating state at time t10. The solid line in this figure corresponds to an example of transition from the high load operation state to the idle state, and the broken line corresponds to an example of transition from the low load operation state to the idle state. As is apparent from this figure, the estimated cetane number CET stabilizes more quickly when shifting from the low load operation state to the idle state, so that, for example, the idle operation state is hardly maintained immediately after refueling while the idle operation state is hardly maintained. When the state is shifted to the state, the complete learning value CETLRNC can be obtained early. Since the wall surface temperature TWALL calculated in step S16 in FIG. 3 increases as the engine load increases, the appropriate time (estimated cetane number CET is stabilized) according to the operation state in the off-idle state by steps S17 to S19. You can start learning at the same time.

  In this embodiment, the fuel injection valve 6 corresponds to a fuel injection means, and the in-cylinder pressure sensor 2 and the ECU 4 constitute an ignition timing detection means. The ECU 4 constitutes cetane number learning means and control means. Specifically, the band-pass filter unit 71, the phase delay correction unit 72, and the ignition timing determination unit 73 shown in FIG. 5 correspond to a part of the ignition timing detection unit, and the process of FIG. 3 corresponds to the cetane number learning unit. 9 and 10 correspond to the control means.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the area ratio RS is used as a parameter indicating the stability of the combustion state, but the Pmi variation rate may be used.
In the above-described embodiment, the actual ignition timing CAFM is detected as the time when the pressure change rate dp / dθ detected by the in-cylinder pressure sensor 2 exceeds the detection threshold value DPP, but is not limited thereto. You may make it determine 50% position of a heat release rate as ignition timing.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. FIG. 2 is a diagram more specifically showing a partial configuration of the control device shown in FIG. 1. It is a flowchart of the process which performs learning of a cetane number. It is a flowchart of the process which performs learning of a cetane number. It is a block diagram which shows the structure of the ignition timing calculation module which calculates (detects) actual ignition timing CAFM. It is a time chart for demonstrating the band pass filter process of an in-cylinder pressure sensor output. It is a time chart for demonstrating the detection method of ignition timing. It is a figure which shows the table for calculating a cetane number (CET) from ignition delay time (TDFM). It is a flowchart of the combustion control according to a cetane number learning value. It is a flowchart of the process which detects that the combustion state of the engine became unstable and switches combustion control. It is a figure for demonstrating the area ratio (RS) which is a parameter which shows a combustion state. It is a time chart which shows transition of engine cooling water temperature (TW) immediately after cold start. It is a time chart which shows transition of the estimation cetane number (CET) when changing from driving | running states other than an idle to an idle driving | running state.

Explanation of symbols

1 Internal combustion engine 2 In-cylinder pressure sensor (ignition timing detection means)
4 Electronic control unit (ignition timing detection means, cetane number learning means, control means)
6 Fuel injection valve (fuel injection means)

Claims (2)

In a control device for an internal combustion engine comprising fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine,
Ignition timing detection means for detecting the ignition timing of the fuel injected by the fuel injection means;
A cetane number learning means for estimating a cetane number of a fuel in use according to the detected ignition timing and calculating a learning value by performing a smoothing operation of the estimated cetane number ;
Control means for controlling the engine including at least control of fuel injection timing by the fuel injection means, using a learning value calculated by the cetane number learning means,
The cetane number learning means stores the calculated learning value as a provisional learning value until the learning of the cetane number is completed, and the continuous estimation number of the cetane number according to the detected ignition timing becomes a first predetermined value. The temporary learning value is stored from the time point reached, and when the number of continuous estimations of the cetane number reaches a second predetermined value greater than the first predetermined value, it is determined that the learning is completed and The learning value is stored as a complete learning value, and the temporary learning value is continuously updated until the learning is completed,
The internal combustion engine, wherein the control means performs the control using the provisional learning value until the learning is completed, and performs the control using the complete learning value from the time when the learning is completed. Control device.   The learning of the cetane number is performed by changing the mode of fuel injection by the fuel injection means when the engine is in an idle operation state immediately after refueling, and after completion of the learning, the learning is performed until the next refueling is performed. The control device for an internal combustion engine according to claim 1, wherein learning of the cetane number is not performed.

Images